Abrasive articles have been utilized to abrade and finish workpieces surfaces for well over a hundred years. These applications have ranged from high stock removal, high pressure metal grinding processes to fine polishing of ophthalmic lenses. In general abrasive articles comprise a plurality of abrasive particles bonded either together (e.g., a bonded abrasive or grinding wheel) or to a backing (e.g., a coated abrasive). For a coated abrasive there is typically a single, or sometimes two layers of abrasive particles. Once these abrasive particles are worn, the coated abrasive is essentially worn out and is typically discarded.
One solution to this single layer of abrasive particles is described in the following U.S. Pat. Nos. 4,652,275; 4,799,939 and 5,039,311. The coated abrasive that is disclosed in these references comprises a backing having a plurality of abrasive agglomerates bonded to the backing. The abrasive agglomerate is a shaped mass comprising abrasive grains, a binder, optionally a grinding aid and optionally other additives. These abrasive agglomerates essentially result in a three dimensional coating of abrasive particles.
Another three dimensional coating of abrasive particles is an abrasive lapping film. A lapping film, like that disclosed in U.S. Pat. Nos. 4,644,703, 4,773,920 and 5,015,266, consists essentially of an abrasive slurry comprising abrasive particles and a binder bonded to a backing. These lapping films have had wide commercial success in polishing applications where a fine surface finish on a workpiece is desired. However, these lapping films do not always have the desired rate of cut for many other applications.
A means to increase the cut rate of lapping films is disclosed in U.S. Pat. No. 5,152,917 (Pieper et al.).
Pieper teaches a structured abrasive that results in a relatively high rate of cut and a relatively fine surface finish on the workpiece surface. The structured abrasive comprises non-random, precisely shaped abrasive composites that are bonded to a backing.
Pieper is a significant advancement in the abrasives art especially for abrading painted surfaces, however there is always room for improvement in abrading metal workpieces.
U.S. Ser. No. 08/120,300, filed Sep. 13, 1993, (Hoopman) discloses articles having shaped composites of differing dimensions.